Electric vehicles (EVs) and plug in hybrid electric vehicles (PHEVs) comprise a bank of batteries and an on-board charger, which converts household AC power to DC power at the voltage required for charging the batteries.
Due to the limited mileage of electric vehicles owners usually prefer to recharge at home while drawing power from the grid via a wall mounted charge station in their garages or car ports. Charging is usually performed overnight in order to provide the full mileage range every day. Typically, charge stations comprise a flexible cable and docking station for the dedicated charge connector as well as various control check and safety components.
In the United States, most wall outlets deliver 120 volt power via a circuit breaker in the household electric panel. The majority of homes also have 240V outlets, located in the kitchen or laundry area, which serve to power ranges, washer/dryers and air conditioners. However, in general, circuits serving the garage are only 120V and wired for 15 or 20 amperes, with one circuit feeding several outlets, and effectively limiting power draw to 1800 or 2400 watts respectively. Until the appearance of electric vehicles, garage power outlets were mostly used incidentally to operate power tools, garage door openers, lighting, etc.
The capacity of the battery bank in an electric vehicle may typically be from 20 to 50 kWh, and fully depleted will require on the order of 10 to 20 hours of charging time when powered from a 120V outlet. This amount of time is generally considered too long by EV owners and for this reason most residential EV charge stations require a dedicated 240 volt outlet, enabling a max power output of 3600 or 4800 VA while still drawing 15 or 20 amperes respectively. Thus, the effect of having a 240V outlet as compared to a 120V outlet is to cut the excessive charging times mentioned above in half.
The need for 240 volts to operate the charge stations available in the market today means that new owners of electric vehicles will have to invest a considerable amount in the installation of a new 240V outlet in the garage area. The cost of the 240V circuit including wiring from the house power panel may well be on the order of $1 000 to $2,000, far exceeding the cost of the charge station itself.
One way of saving the extra cost of a new 240 volt outlet is to convert the original 120V circuit to 240V. The conversion can be done inexpensively without additional wire drawing by exchanging the single circuit breaker in the power panel with a double circuit breaker, thereby converting the former neutral wire in the circuit to a hot wire. However, a negative effect of the conversion is the loss of the 120 volt outlets in the garage area, which were served by the former 120 volt circuit.
There are currently no known charging stations that remedy this problem.
Although several prior art U.S. patents and published patent applications, including U.S. Pat. Nos. 8,072,184 and 8,013,570 and U.S. Patent Application Publication Nos. 2011/0174875 and 2011/0140656, disclose charging stations for electric vehicles having, in some embodiments, charging cords or outlets for charging at 240V, and also charging cords or outlets for charging at 120V, the disclosed charging stations are generally not compatible with the retrofit situation where a home owner desires to convert an existing 120V circuit to 240V without having to pull new wires. None of the references is at all concerned with any type of retrofit method all, and thus according to the references, it is perfectly acceptable for the 240V portion of the charging station to be fed power from a 240V power source, and for the 120V portion of the charging station to be fed power from a separate 120V power source.
Obviously, requiring two separate power sources would completely defeat the purpose of the above-described retrofit method, the crux of which is to allow a single existing 120V circuit to be converted to 240V without pulling additional wires.